Water-dispersible preparations of fat-soluble substances, e.g. the fat-soluble vitamins, carotenoids, polyunsaturated fatty acids and the like, play an important role in the field of human and animal nutrition. Such preparations are usually marketed in the form of emulsions or dry powders because of their water-insolubility or also their more or less pronounced stability and ease of handling. It is a common feature of such preparations that the active substances, i.e. the fat-soluble substances, are usually enveloped with a matrix component (protective colloid), e.g. gum arabic or gelatine. This matrix component is responsible, inter alia, for the protection of the active substance or for its stabilization, for an optimum resorption and for the water-dispersibility of the final preparation which may be required. As the matrix component (protective colloid) there is normally used gelatine which originates from warm-blooded animals and which accordingly also has certain disadvantages. Merely by way of example there are to be mentioned here the fact that preparations based on such gelatine cannot be used worldwide for religious reasons, that without an expensive production process this gelatine and accordingly also the pulverous preparations manufactured therewith do not always have the desired dispersibility in cold water, etc. To overcome such drawbacks inherent to gelatine-base preparations the use of certain lignin derivatives as a matrix component instead of gelatine has been proposed, see, e.g., U.S. Pat. No. 5,668,183. A preferred process for the manufacture of such lignin derivative-based powderous preparations is the starch-catch process which is a spray-drying process where the sprayed emulsion particles are collected in a bed of starch. The so-obtained products consist of particles comprising the matrix component and the fat-soluble substance embedded therein which are covered by an adhesive layer of starch. The term “beadlets” as used herein refers to such particles.
Beadlets provide superiour handling properties in that they are not dusty and possess good flowablity characteristics. However, the production of lignin-derivative based beadlets and, generally, beadlets based on non-gelling matrix components, by the starch-catch process as described is accompanied by the formation of deposits in the spray tower which requires an interruption of the spray-drying process for cleaning the installation. It has now been found that the formation of deposit in the spray tower can be significantly suppressed or substantially avoided when a stream of cold air is introduced into the lower part of the spray tower, thus forming a fluidized bed which has a substantial lower temperature than the temperature of the spray zone, whereupon the beadlets are discharged from the fluidized bed to a dryer to complete the drying process.
Accordingly, in one aspect, the present invention relates to a process for the manufacture of beadlet preparations of fat-soluble substances in a water-soluble or water-dispersible non-gelling matrix, which process comprises
(a) feeding in the upper section of a vertical spray tower, through a spray nozzle an aqueous emulsion of said fat-soluble substance(s) and said matrix component, and, through separate inlets, powderous starch and a stream of hot air,
(b) feeding in the lower section of said spray tower a stream of cold air to form a fluidized bed of starch-covered beadlets comprising said matrix component said fat-soluble substances, and
(c) collecting said beadlets from the fluidized bed and discharging them to a dryer.
In a further aspect, the present invention relates to an arrangement of nozzles substantially as shown in FIG. 2.
In still another aspect the present invention relates to an installation substantially as shown in FIG. 1.